In atomic absorption spectroscopy a sample is atomized by a flame or by an electrically heated furnace, so that the elements contained in the sample are present in their atomic state. A measuring light beam from a light source which emits characteristic resonant lines of a looked-for element is passed through the atomic vapor generated in this way. Each of the atoms absorbs only radiation with the resonant lines being characteristic of one element. Light having other wavelengths is not absorbed by the atoms of the atomic vapor. Thereby, the measuring light beam is subjected to an absorption which is a measure of the number of the atoms of the looked-for element in the atomic vapor.
The light source is usually a hollow cathode lamp in which a gas discharge with the atoms of the looked-for element takes place. These hollow cathode lamps emit the spectrum of the looked-for element. From this spectrum, a certain resonant line is chosen by a monochromator. The measuring light beam with this resonant line is passed through the atomized sample and impinges onto a photoelectric detector, usually a photomultiplier. With such an arrangement only one single element, at a time, can be measured.
Atomic absorption spectrometers are known in which several different hollow cathode lamps are arranged on a rotatable carrier. One of these hollow cathode lamps, at a time, is moved into an operative position in which it generates the measuring light beam. Thereby, different elements can be measured consecutively. In analyses with electrothermal atomization of the sample in an electrically heated furnace, a separate sample has to be introduced into the furnace for each determination.